Current practice in the automobile industry is to protect electrical and electronic equipment installed in automobiles by means of fuses located in the fuse block in the glove compartment or under the dashboard of the automobile. These fuses are, for the most part, relatively low amperage and are designed to protect apparatus such as radios, lights, and turn signals. Also, these fuses operate in a temperature controlled environment since they are inside the passenger compartment of a car.
Many of the major electrical loads in an automobile are found underneath the hood of a car, such as the starter, alternator, and the battery, to name several. These electrical apparatus draw relatively high currents compared to the typical fuse located under the dashboard. If these underhood electrical apparatus were to be protected by fuses mounted in the passenger compartment, the wiring connected to them would have to be routed through the firewall to the passenger compartment to the fuseblock and then back through the firewall to the component under the hood. This, of course, would add weight to the automobile, additional labor costs, and increase the cost of production. It is, therefore, desirable to locate some circuit protector under the hood of automobiles.
It is preferred to group these large automotive fuses together in one location under the hood in a fuseblock. Since different components under the hood of an automobile have different operating and starting characteristics, it follows, naturally, that fuses of different amp ratings and characteristics will be inserted in the fuseblock. However, in order to standardize the shape of the fuseblock so that it can be used in different model automobiles requiring different combinations of fuse ratings, the large automotive fuses have been standardized as to size and shape. Therefore, potential problems exists in that an improper rated fuse may be inserted out of order and open at too low a current or a fuse with too high a rating may be inserted in the improper order and not protect downstream components.
Manufacturers realizing that this is a problem have verified that fuses are inserted in the proper order by visually verifying location of fuses. However, this method is labor-intensive in that it requires an extra worker on the assembly line.